55728921 has 4 divisors (see below), whose sum is σ = 74305232. Its totient is φ = 37152612.

The previous prime is 55728901. The next prime is 55728947. The reversal of 55728921 is 12982755.

55728921 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is not a de Polignac number, because 55728921 - 2⁵ = 55728889 is a prime.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 55728921.

It is not an unprimeable number, because it can be changed into a prime (55728901) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 9288151 + ... + 9288156.

It is an arithmetic number, because the mean of its divisors is an integer number (18576308).

Almost surely, 2^55728921 is an apocalyptic number.

It is an amenable number.

55728921 is a deficient number, since it is larger than the sum of its proper divisors (18576311).

55728921 is a wasteful number, since it uses less digits than its factorization.

55728921 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 18576310.

The product of its digits is 50400, while the sum is 39.

The square root of 55728921 is about 7465.1805738374. The cubic root of 55728921 is about 381.9679098250.

The spelling of 55728921 in words is "fifty-five million, seven hundred twenty-eight thousand, nine hundred twenty-one".